Computer Networks

Fundamentals of Computer Networks

Learning Objectives

• Concepts of Networking:
    - LAN (Local Area Network)
    - WAN (Wide Area Network)
    - Intranet
    - The Structure of the Internet

• Understanding IP Addressing and DNS:
    1. The role of IP addresses in transmitting data:
       - Data communication is the process whereby two or more devices exchange information.
       - Essential for enabling communication on the Internet.
    2. Details on IPv4 and IPv6:
       - IPv4: 32-bit address space, limited to approximately 4.3 billion unique addresses.
       - IPv6: 128-bit address space, theoretically allows for approximately 3.4 x 10^38 unique addresses.
    3. Static vs. Dynamic IP Addresses:
       - Static IP: Permanently assigned by an administrator.
       - Dynamic IP: Assigned temporarily by a DHCP server, changes frequently.
    4. Purpose of subnetting:
       - Enhances network efficiency by reducing the distance data must travel through routers.
    5. Role of DNS in website access:
       - Maps Fully Qualified Domain Names (FQDN) to IP addresses for easy access.

• Communication Protocols:
    1. Importance of protocols in networks:
       - Example protocols include TCP/IP, FTP, and SMTP.
       - Different protocols serve various purposes, facilitating tasks like file transfer, email transmission, and web hosting.

• Packet Switching:
    - Explanation of the process in packet-switching networks for data transmission.

• Client-Server Architecture:
    - Definition and roles of nodes in networking:
      - Node: Any address-enabled device in a network (e.g., computers, printers).
      - Client: Requests services from the server.
      - Server: Provides services to clients once requests are made.

Types of Computer Network

• Network Applications: Used daily for messaging, browsing, and multimedia streaming.

• Personal Area Network (PAN):
    - A small network for communication between nearby devices, typically within 10 meters (e.g., Bluetooth between phone and headset).

• Local Area Network (LAN):
    - Connects a limited number of devices within a small geographical area (e.g., a school).
    - Commonly uses Ethernet technology for connection.
    - Advantages: High data transmission speeds over short distances.

• Wide Area Network (WAN):
    - Connects multiple devices over a large geographical area, utilizing long-range data links.
    - The Internet is the largest example of a WAN.

• Metropolitan Area Network (MAN):
    - Connects users and resources over a larger area than a LAN, smaller than a WAN.
    - Efficient communication via high-speed carriers (e.g., fiber optics).

• Client-Server Network:
    - Centralized servers provide services to multiple clients.
    - Connection is established when a client requests communication, terminating once the request is fulfilled.

Applications of Client-Server Network

• File Server (FTP):
    - Central repository for data storage accessible by multiple clients.

• Web Server:
    - Hosts websites and responds to client requests; reliability increases when fewer websites are hosted.

• Mail Server:
    - Manages sending and receiving emails, often involves complex protocols for functionality (SMTP, POP3, IMAP).

Client-Server Network Advantages and Disadvantages

• Advantages:
    - Better security via centralized file storage and access management.
    - Central backups reduce user responsibility and improve data recovery processes.
    - Enhanced data sharing capabilities among users.

• Disadvantages:
    - High installation and management costs with reliance on IT professionals.
    - Risk of server overload from multiple simultaneous requests.
    - Server failure leads to complete access disruption for clients.

Data Processing in Client-Server Architecture

• Client-Side Processing:
    - Processing occurs on the client device to reduce server load (e.g., data validation via JavaScript).

• Server-Side Processing:
    - Handles larger volumes of data and complex processing tasks (e.g., SQL for database queries).
    - Validates data entries against server databases.

Peer-to-Peer (P2P) Network

• Definition:
    - A structure where peers share resources without a dedicated server (e.g., Napster).

• Advantages:
    - Straightforward setup, cost-effective implementation, and no single point of failure.

• Disadvantages:
    - Individual backup responsibilities for each device, less security compared to client-server models.

Wireless Network

• Description:
    - Allows communication without physical connections, using wireless access points and adapters.

• Wi-Fi:
    - A widely used standard enabling device connectivity worldwide.

• Advantages:
    - Mobility, efficient scalability, and accessibility.

• Disadvantages:
    - Vulnerable to security risks and issues with interference affecting communication quality.

Network Devices & Transmission Media

• Definition:
    - Network devices facilitate communication in a computer network.

• MAC Address:
    - A unique identifier for network devices, hardcoded into network interface cards (NICs).

• Network Interface Card (NIC):
    - Essential for connecting devices to a network, required for all devices.

Key Network Devices

• Hub:
    - Central device for connecting multiple computers; broadcasts data to all connected devices simultaneously.

• Switch:
    - Routes data to the correct MAC address, improving efficiency over hubs.

• Router:
    - Connects different networks and routes packets based on IP addresses.

• Bridge:
    - Connects multiple LANs, extending the network capacity.

Routing Process

• Routing:
    - The process of selecting paths for data to travel from source to destination.

• Routing Algorithms:
    - Software determining optimal paths using metrics (e.g., hop count, bandwidth).

Data Communication and Transmission

• Transmission Media:
    1. Cable Media:
       - Twisted-pair, coaxial, and fiber-optic cables.
    2. Wireless Media:
       - Uses electromagnetic signals for transmission.

• Data Transmission Modes:
    1. Simplex Mode: Unidirectional communication (e.g., keyboard to monitor).
    2. Half Duplex: Bidirectional but not simultaneous (e.g., walkie-talkies).
    3. Full Duplex: Simultaneous two-way communication (e.g., telephones).

Networking Protocols

• Definition: Rules governing message transmission and data packet management.

• TCP/IP Model Layers:
    1. Application Layer: Interfaces with users and applications (e.g., FTP, HTTP).
    2. Transport Layer: Manages data transfer (e.g., TCP, UDP).
    3. Internet Layer: Handles IP addressing and routing.
    4. Link Layer: Addresses physical transmission (e.g., Ethernet framing).

Application of Protocols

• User Datagram Protocol (UDP):
    - Connectionless protocol; suited for time-sensitive applications (e.g., streaming, gaming).

• Transmission Control Protocol (TCP):
    - Ensures reliable data delivery through error checking and resending lost packets.

IP Addressing

• Definition: Unique identifiers for devices on the Internet.

• Static vs. Dynamic:
    - Static IP addresses are manually assigned while dynamic addresses change periodically.

• Subnetting: Divides networks for efficiency.

• Virtual Private Network (VPN): Provides secure, encrypted connections over the Internet,
   improving privacy and security.

Intranet vs. Extranet

• Intranet: A private network for internal organizational use.

• Extranet: Extension of intranet services to external parties like clients or partners.

Domain Name System (DNS)

• Function: Converts domain names into IP addresses, facilitating web navigation.

Exercises

1. Describe uses of a device.

2. Explain client-side and server-side scripting with examples.

3. Discuss advantages of intranet over the Internet for catalog access.

4. Differentiate between LAN and WAN and hardware uses in networking scenarios.